Creatures

All About Hammerhead Sharks

Of all the sharks that swim in the oceans of the world, perhaps none have piqued our collective interest more than the fascinating hammerhead shark.

When you see different kinds of sharks, it can be confusing to tell them apart.  There are 440 known species of shark, after all!

That said, hammerheads are usually easy to distinguish from other sharks, mainly because of their large hammer-shaped heads.

Now why is it, people often ask, that hammerhead sharks have a head that has this odd shape?  We will get to that soon enough, as the answer to this question is quite remarkable, if not exactly obvious.

First, though, we should talk about some of the more frequently asked questions about hammerhead sharks…

What are the different types of hammerhead shark?

There are 9 species of hammerhead, including:

  1. Bonnethead
  2. Great Hammerhead
  3. Winghead Shark
  4. Scalloped Bonnethead
  5. Whitefin Hammerhead
  6. Scalloped Hammerhead
  7. Scoophead
  8. Smalleye Hammerhead
  9. Smooth Hammerhead

Here is a picture showing the variously different head types.

As you can see, the head shapes vary greatly, and so calling some of these sharks ‘hammerheads’ might be a little bit misleading.

Actually, I’d say that a lot of these sharks’ heads look more like an anchor than a hammer.  What do you think?

In any case, there is no petition to change the name yet, as “hammerhead” seems to have stuck.

Dare to compare!

How Big is a Hammerhead?

While there are bigger sharks in the water, such as whale sharks, tiger sharks, and pacific sleepers, hammerheads are not exactly the small fry of the bunch.

In terms of size, the largest hammerhead, as you might have heard, is the Great Hammerhead, which can reach up to 6 meters long as a fully grown adult (that’s almost 20 feet), and weighing up to 170 kilograms (or 600 pounds).

The rest of the hammerhead species are smaller than this, averaging 4 meters long and proportionately less in terms of weight.

The smallest hammerhead is the bonnethead, which only grows to approximately a meter and a half long, or 5 feet.

Now this is a kind of shark that some might even call “cute”.

How long do they live?

Hammerheads are known to live up to 20-30 years old, if we don’t force them into captivity.  If they are free to swim the seven seas, they will live much longer, as all free creatures do appreciate the ability to roam and not be trapped.

In particular, hammerheads do need their freedom, because they absolutely need to keep moving in the water, or they will sink and die.

Where do hammerheads live?

Hammerheads love warm, tropical waters, and so this results in them staying closer to the surface of the water where the sun can give them their characteristic “tan”, and so they also avoid the deeper, darker parts of the ocean.

If there is a reef, or a coastline, you may find hammerheads there.  They can swim in water that is just 1 meter deep, and can venture out to depths of 80 meters, but rarely beyond that depth.

As this map below shows, hammerhead habitats can be found all over the world.

As there are 9 different species of hammerhead, you will find them everywhere that that suits their fancy.  These areas include various shallows, inlets, reef areas, and continental shelves.

The reason hammerheads love these areas is partly due to the abundance of food, with all manner of tender morsels living in these zones.

What do hammerheads eat?

In many ways a hammerhead is a typical shark, in that it is a predatory fish that is carnivorous.

Generally speaking, when it comes to food, hammerheads love to eat things like octopus, other fish, stingrays, squid, crustaceans, and, sometimes, other sharks, including their own offspring.

With certain creatures, like stingrays, hammerheads will use their head to pin the stingray to the ocean floor, preventing a sting from occurring, then they bite their prey to injure it.

Similar to a dog with a chew toy, the hammerhead will then wring their prey from side to side, and eventually eat it once it stops fighting back.

Here is a video showing a hammerhead trying to catch a stingray.

https://www.youtube.com/watch?v=pWiH7tfjKTo

Because of where hammerheads are typically found (that is, in shallow, warmer areas where humans like to swim), they are generally seen to be “friendlier” than your average Great White, who is seen very often as a man eater.

Because they linger in beautiful reef areas, with other fabulous fish, it isn’t unusual for divers to encounter them, and actually be around them without fear.  In fact, many divers are out there actively looking for hammerheads so they can touch them and take pictures of these interesting creatures.

Here is a video showing scuba divers interacting with hammerheads in the Bahamas.  Video by Becky Kagan Schott.

https://www.youtube.com/watch?v=JeHAHPERQjk

This leads to our next question…

Are hammerhead sharks dangerous?

While some people think hammerheads are more nonthreatening because of their strangely shaped head, hammerheads are indeed sharks, and that means they like meat.  If they smell blood in the water, they will investigate it.

They are a very sensory-driven fish, and they can sense motion at long range, tracing electrical pulses through the water, including heart beats.  Their vision is panoramic, due to their wide set eyes, so they can see everywhere all the time.

Their sense of smell is also keen, but not as keen as you might think because of their wide noses.  They have a similar sense of smell to other sharks, basically.

In terms of their mouths, you can see by looking a a hammerhead’s mouth that it is not as scary as that of a great white shark.

For instance, here’s a hammerhead’s mouth and teeth.

…here’s a Great White’s mouth and teeth.

Clearly, one shark definitely seems a little scarier.

All the same, hammerheads are relatively unthreatening to humans, unless you meet up with an aggressive one.

It’s true to say that the number one threat to hammerheads is most certainly humans, who sometimes hunt them for their meat, or simply for sport.

Read our article, How To Say Shark in 45 Languages

On the flipside, hammerheads basically pose no threat to humans.

For instance, the bonnethead that we mentioned before is considered to be “shy” and really wants nothing to do with people.

Heck, even the Great Hammerhead, at the end of the day, has not been known to attack humans.  Or, at least not very often, though there have been recorded cases here and there.

As it stands, the only hammerheads who have EVER attacked a human are the Great Hammerhead, the Scalloped Hammerhead, and the Smooth Hammerhead.  The rest have not.  We cannot say what caused these attacks, either.

Here’s a hammerhead attempting to gnaw on a man’s kayak.  Does the shark think the kayak is a large fish?  Is the shark just “playing” or feeling frisky?  You be the judge…

https://www.youtube.com/watch?v=eoiWtj-N49w

Generally, our research shows that hammerheads are not what you would call dangerous.  At the same time, we are NOT saying it’s a great idea to go and play with the next hammerhead shark you see.

Hammerhead Behaviour

Hammerheads can be found alone, or in packs which are called “schools”.  These schools will get together during the daytime, leaving hammerheads on their own at night to hunt.

Galapagos is a popular location for hammerheads to congregate.  Here is a video showing a hammerhead school.  As you can see, the hammerheads are not very concerned about the human’s presence, although you can be sure that they know the human is there watching them.

https://www.youtube.com/watch?v=iV0caINnnWE

The purpose of these schools is to meet up for migratory purposes and social interaction, especially mating.

For instance, in the summer months, when it’s hotter, hammerhead schools will get together and travel to a cooler location, where they can then have a high number of mates to choose from, as they have already assembled into a large group for travelling.

For the record, hammerhead youth are called “pups”.  The duration of a hammerhead pregnancy is 14-16 months, which is longer than the Great White’s 11 months gestation period.

Here is a video showing some jackass pulling a hammerhead onto shore while it gives birth.  DO NOT DO THIS.  Hammerheads need to be left alone to their own devices, not dragged out of the water, especially while giving birth.

https://www.youtube.com/watch?v=RSQbttD0C1I

Physiology

As mentioned, a hammerhead shark has wide set eyes that are some of the best in the ocean for seeing what’s going on.

Their eyes are similar to a human’s eyes, in that they see together as opposed to independently.

The interesting shape of their head has puzzled humans for decades, but it has been determined that the reason their head is shaped this way, is to increase the hammerheads’ agility in the water, allowing them to use their head as a rudder to turn quickly, as well as perform other agile motions.

Because the hammerhead doesn’t have overly large pectoral fins, their large head helps to compensate.

This, overall, makes the hammerhead a better predator as they can not only see very well, but, due to the size of their head, there are plenty of receptors that they use to detect prey.

All sharks use these receptors to detect different motions in the water at great distances, but a hammerhead has been blessed with more of these receptors, and so this gives them an advantage over other predatory fish.

https://www.youtube.com/watch?v=PPGomiSf-t8

If you watch a hammerhead in action, you can see that it appears to be “sniffing” the sand a lot of the time, as it travels on the ocean floor…. most likely looking for rays to munch on.

Why Do Hammerheads Need To Keep Moving?

Hammerheads must swim in order to breathe.  As we mentioned earlier, if a hammerhead stops swimming, it will sink, and hence become immobilized.  Imagine that you decide to stop moving your arms and legs.  You wouldn’t be able to get any food to stay alive, because you’d be stuck in one spot.

More than that, though, hammerheads need to extract oxygen from the water by having it pass over their gills, like other sharks.  So, if they don’t move through the water, they can’t extract oxygen, and hence they can’t breathe unless they’re moving.

Skin and Bones

Hammerheads also have very interesting skin and bone structure.  Like other sharks, hammerheads have skeletons made of cartilage, rather than bone.  Cartilage heals faster than bones and has many advantages, such as flexibility.

Their skin doesn’t damage easily, and, because they swim close to the water’s surface a lot of the time, they often get a nice “tan” from the sun, allowing them to appear a dark grey from the top view.

Some scientists are particularly interested in hammerheads to see how we can adapt some of their skin characteristics to prevent skin disease in humans, since hammerheads aren’t applying any sunscreen to fend off the sun’s rays and don’t seem to get skin cancer.

There have even been claims that shark cartilage is good for treating cancer, although this hasn’t been conclusively proven.

Galapagos

As mentioned, one very popular spot for hammerheads to congregate is the Galapagos Islands.  Here, there are lots of things for hammerheads to eat, as it is known for its bio-diversity ever since the time of Charles Darwin.

One reason hammerheads come here is to get “cleaned”.  Yes, Darwin Island is a place where the hammerhead encounters the king angelfish, with whom the hammerhead has a symbiotic relationship.

The hammerhead, over time, gets parasites on its body, and it just so happens that the king angelfish likes to eat those parasites.

So, from time to time, hammerheads allow the king angelfish to feed on the parasites, while the hammerhead benefits from a nice cleaning.

Hammerheads are picky about which king angelfish are allowed to nibble on it’s exterior, but eventually, they find the right one and the process commences.  The hammerhead never feeds on the king angelfish, showing some proper respect.

Here’s a video showing this process in action, as well as showing scientists tagging hammerheads for scientific purposes.

https://www.youtube.com/watch?v=jMVziqKUkVI

Conclusion

Hammerhead sharks fascinate us, and always will!  There are always new secrets to be revealed with this mysterious and alluring shark.  Hopefully, by now you can see that just because a hammerhead is a shark, doesn’t mean it’s nasty!  It’s a beautiful creature and should be appreciated.  Thanks for reading!

PS: We all need to raise shark awareness.  Here are some shark related resources we think you will appreciate if you love sharks:

https://defenders.org/sharks/basic-facts

https://www.conservation.org/act/Pages/shark-facts

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